EXPERIMENTAL STUDY ON THERMAL PERFORMANCE OF OPEN LOOP GROUND SOURCE HEAT PUMP SYSTEM

Abstract

The predicted end of an oil era, along with increasing concentration of carbon dioxide, nitrogen, and dust particles causes pollution in our environmental system. This results in climate changes of earth leading to rapid increase in global warming effects. This has forced us to explore the urgent need of alternative renewable energy sources. In these context Ground Source Heat Pump (GSHP) systems has attracted the researchers because it is green, sustainable and environment-friendly energy source option. GSHP systems are considered very efficient for space heating and cooling applications as they interact with the ground which has constant heat source/sink temperature throughout the year, resulting in improved performance compared to the conventional climate control systems which interact with the atmosphere. As part of the present MTech dissertation work, an attempt is made to study the performance of an open loop GSHP system for space cooling and heating applications. In the open loop GSHP system the heat interaction between the heat pump and the ground takes place through a plate heat exchanger, which enables heat transport between the water coming from the heat pump and the ground water extracted from a bore well drilled for this purpose. After absorbing heat from the coolant from the heat pump, the ground water is re-injected back into another injection bore well. The thermal performance of an open loop GSHP system depends on the groundwater flow rate, temperature of extraction and injection groundwater, power consumption by compressor and pumps and efficiency of plate heat exchanger etc. Experiments were conducted on an 8 TR open loop GSHP system established in the dining hall of the guest house in NETRA (NTPC Energy Technology Research Alliance), Greater Noida during space cooling and heating operations. A computer program in FORTRAN has been developed to calculate COP and effectiveness of plate heat exchanger using the experimental data. Results were obtained for the experimental data observed during 23rd May, 18th July and 19th July 2018 for space cooling mode and show that the COP of the GSHP system varied from 3.48 to 3.92 whereas the effectiveness of the plate heat exchanger varied from 0.72 to 0.75. During winter season, on 28th, 29th and 30th January 2019, the results indicate that the COP of the GSHP system varied from 4.2 to 4.5 and effectiveness of PHE varied from 0.70 to 0.74. Based on theoretical analysis, with the assumption of average combined efficiency of submersible pump as 34.5%, it is observed that if mass flow rate of groundwater increases then the overall heat transfer coefficient, power consumption by submersible pump and COP of the system increases whereas effectiveness of PHE decreases.